Early in the game, you want to stay passive with the majority of the races and not ally. Maintain your position, and establish your defenses and trade partners. Remember, if you're going to setup a system, you should fully develop that system before moving on.

Terraforming your planets is absolutely important, especially midgame. This will allow you to make colonies with maximum spice production.

When looking for systems to colonize, remember to look for systems with multiple types of spices. Easier on you so you can trade them. If it is already occupied by a sentient species (one that is in a non-space stage), my suggestion would be to just wipe them out and take the system. More types of spices = easy to get tons of money.

Artifact Hunting is a great source of income early when you don't have alot of spice production going. Look for these early on to give you an early boost.

How you play early on does affect your game later on, in terms of special abilities. You can change these, but it costs money.

Setting up trade routes eventually allows you to take over a friendly species system. They will offer it up for sale, and you will name a suitable price (depending on how valuable the system is).

If you find an enemy colony on a non-T1 planet, just blast it. It's more profitable to just take that extra money you gain from destroying ships/colonies then terraforming, recolonizing, etc.

Enemy T3 planets are very hard to take over, but very rewarding. Try not to destroy the planet unless you absolutely have to.

Honestly I go with both a Peace bringer type of play and Warmonger type of play as I prefer to attack any that is weak and ally strong Alien races. The way I do it is that I colonize a lot of planets that way no matter what I still get to the weapons or items I need and get alot of cash out of it. I honestly find it money draining to Terra form all the planets so I actually let a few not be terra formed.

Honestly I go with both a Peace bringer type of play and Warmonger type of play as I prefer to attack any that is weak and ally strong Alien races. The way I do it is that I colonize a lot of planets that way no matter what I still get to the weapons or items I need and get alot of cash out of it. I honestly find it money draining to Terra form all the planets so I actually let a few not be terra formed.

I registered just to say that I stumbled upon this guide through Google because I needed one for a non aggressive creature history for Spore (surprisingly hard apparently) since I've really started getting into Spore style games again.

I found it really helpful and even though the post is several years old the strategies still hold true and helped me alot. It's not always a bad thing keeping outdated forums!